AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Influence of Evaporation Rate and Suspended Solid Concentration on Dry Particle Formation from Evaporating Aerosol Microdroplets
JUSTICE ARCHER, Florence Gregson, Daniel Hardy, Jim Walker, Rachael E.H. Miles, Jonathan P. Reid, University of Bristol
Abstract Number: 45 Working Group: Aerosol Chemistry
Abstract The evaporation of aerosol droplets containing suspensions of submicron solid particles is encountered in various engineering fields, e.g. pharmaceutical industry, bioengineering, food industry and cosmetics. Most often, the evaporation of such systems leads to the aggregation of the suspended solid particles in the droplet into a solid structure at the end of the evaporation process. Understanding what controls, the final morphology of the aggregated particle is therefore a key issue for most industrial applications. The droplet evaporation kinetics during the evaporation process, as well as the morphology of the final dry solid particle structure, is highly dependent on factors such as variation in ambient temperature and relative humidity, the initial droplet composition and size, as well as the properties of the suspended submicron solid particles.
In this work, we explore how evaporative parameters (controlled atmospheric conditions – relative humidity and temperature) and the initial droplet composition (solid inclusion size and concentration) affect the droplet evaporation kinetics and the morphology of the final dry structures both during and after the evaporation process on a per-drop basis. An Electrodynamic Balance (EDB) is used for droplet kinetics measurements under tunable atmospheric conditions (265 – 325 K, 0 % to ~95 % RH) and for variable droplet parameters (droplet radius 25 - 30 µm; inclusions-hydrophilic silica beads, 12 nm in diameter at concentrations, 0.1 – 0.5 % v/v). Additionally, a falling droplet-chain instrument is used for final dry particle collection and offline-scanning electron microscopy (SEM) imaging used for final dry particle observation. Our aim is to provide a comprehensive experimental study resulting in an improved understanding of the influence of evaporative and inclusion parameters on the evaporation kinetics and morphology of final dry products, particularly those encountered in spray-drying processes.